Synch/idle issues

So looks like I've still plenty to learn about being a motorbike mechanic. After pulling the carbs apart, putting them back together, adjusting the float levels (clear tube method), bench synching, synching with a carbtune, trying to get the mixtures right I've not got it right yet.

Couldn't get a satisfactory sync and on some settings the idle would race. Tested for air leaks with propane but could not find anything. After cleaning and relubing throttle cable and cleaning the gummed up handle bar where the throttle tube sits the throttle releases with a clunk back to idle but noted at the carb end there seems to be a bit of binding or stiffness releasing all the way back (like the last 1mm or so).

So after much frustration yesterday I've pulled the carbs off the bike, separated them and am going to check over everything.

What I discovered was I'd pinched a fuel pipe seal between 3 & 4 and there was some contamination in the throat of number 3 carb from the rubber boot - probably from when I put the rack back on the bike. I also noted that #4 butterfly valve was not seated quite flush and a little light was leaking past it





So the plan of attack is:
Replace fuel pipe seals again - this time use a little lubricant prior to installing
Check #3 carb and make sure it's still clean
Redo clunk test - just to make sure
Check and if necessary re-seat butterfly valves
Test each individual throttle valve mechanism and then check function as a whole prior to locking rack back together.
Check float levels again (arrgghhh)
Clean out airbox & boots

Had intended to ride down to East Gippsland this Melbourne Cup weekend but think time may be against me.

If anyone has any tips or knows of something I've missed let me know.

 

always goose the throttle after each screw adjustment. sometimes it takes 3 or 4 tweaks after each throttle goose before it snaps back to level with throttle goose.

if you just make the adjustments and don't goose the throttle. you'll find the sync not holding when you go riding.

you adjust the screw. make things level. but goose the throttle you'll find it's still off when throttle comes back to idle. give another tweak. goose the throttle. keep doing untill it comes back to level each time.

 

Have you replaced the shaft seals?

 

Yep, shaft seals replaced first time around.

 

you said, "noted at the carb end there seems to be a bit of binding or stiffness releasing all the way back (like the last 1mm or so).
Is it still like this now that the carbs are off the bike?
Lay a straight edge across the inlet and outlet to see if the carbs are straight.

 

Leave the butterfly screws loose until the rack is bolted to the rails, remember to lay the rack on a length of angle iron (or something FLAT), even cramping the rack down while you do up the screws, fix the butterflys in the fully closed possition, make sure they are seated evenly all around.

 

No, now the carbs are separated the throttle shafts are bringing the butterflies closed nicely. Maybe I've overtightened the nuts used on the throttle shaft of the carbs that have them or maybe it was a symptom of poorly aligned butterfly valves.

I've a piece of 450 x 450 6mm acrylic as the flat sheet to align the carbs and will leave the butterfly screws loose this time until secured together.

At least this is taking my mind of having to spend money on a new freezer over the weekend, after our 20 year old model finally carked it, thereby putting paid to my brake rebuild project for awhile

 

Right first major problem. Carb 1 has a pinhole in the diaphragm rubber. Damn looking back at the project this is one thing I overlooked checking.

If anyone has any tips to repairing these please let me know. Looks like cost of replacing them is pretty high.

 

Rubber cement can you post some pics of the things you find that are wrong

 

i read somewhere a piece or sheet rubber ( maybe an intertube) and liquid electrical tape will fix your diaphram.

 

I have fixed pin holes with RTV, rough up each side with 400 grit paper & poke the RTV throgh the hole with a toothpick, so it mushrooms out on both sides (like a rivet)

 

when you put the rails back on, just snug the screws till they touch then snap the throttle a few times on the flat plate, then snug the screws again and snap the throttle again then tighten them, this lets the throttle shafts find their own center
i use the same method for the butterfly plates
when you bench sync try using the little holes on the top engine side of the bore as a guide, i think it's a little easier

 

I've school tonight so will not have a chance to look at the bike till tomorrow. I'll take pics then and post up.

wiz, what's RTV?

Found this thread on a Kawasaki forum: http://www.kawasakimotorcycle.org/forum ... works.html
The poster there is suggesting Gorilla Glue works well on the Kawasaki diaphragms which are a Nitrile rubber.

 

I used a few thin coats of rubber cement.

 

RTV is the caulk material you squeeze out of a tube and it Vulcanizes at Room Temperature. Also known as silicone caulk, donkey dribble, gorilla snot, etc. It's the rubbery stuff used to seal around your bathtub.

Loren

 

So sounds like Gorilla Glue or Gorilla Snot is the way to go lol

 

Bathtub? you have to wonder, RTV, room temparature vulcanizing, get it from your local Repco, or Supacheap.

 

A product called "Liquid Electrical Tape" works like magic but I don't know if you can get it there.

 

Picked up some Liquid Electrical Tape today from Jaycar. Will do some testing and hopefully lay it on tonight.

Here's a picture of the hole, really a small tear rather than a hole:

 

With a tear you might have to introduce a piece of condom (the black russian works well)

 

Never new condoms were impervious to petrol, well there you go!

 

not something you would think about, reallly

 

Well things are worse than I first thought. Checked over the diaphragm again tonight and found a couple of other pinholes. Now I'm thinking I may have stuffed them up storing them for 4 months in ziplock bags and whilst I was careful not to get any cleaner on them maybe the diaphragm was contaminated in some way.

Well I found this post http://www.xjbikes.com/Forums/viewtopic ... tml#152343 so see what we can do.

 

Hey Crow
I recently got my '84 XJ900 back on the road after a full carb rebuild.
3 of 4 diaphragms had multiple holes.
I used a liquid rubber product called "PlastiDip" & small pieces of "nitrile" surgical gloves to patch them.
I have only done about 1500Ks since, but all seems good at the moment.
I think the repair is worth a try.
Here's a link to "PlastiDip" if you're interested:
http://stores.shop.ebay.com.au/Plastidi ... QQ_armrsZ1
I used the flexible rubber aerosol.
Give it a go mate & good luck.

 

I bought liquid electrical tape today so am going to give that a go but thanks for the info.

Well good news is carbs #2 - #4 diaphragms are OK but I noticed where the plastic clip is cracked on each one there is certainly a vacuum leak there. I'll look at plugging that up with RTV or Gorilla Glue.

Also found the o-ring for the pilot mixutre screw was broken in two. Looks like I may have not seated it flush or it was defective (brand new as well)

All passed the clunk test although now they're off again I will hit them with a couple of scotchbrite pads.

Wife wouldn't let me cut her funnels so off to buy them and paintbrushes tomorrow.

 

Are you using lubricant on your orings when you install them? As far as the clip ive tried several different glues but never found anything that would hold, anyone ever have any success repairing them?

 

No it's one of the things I didn't realise I should do. Will use a silicon lubricant on the fuelpipe o-rings this time round.

 

The following technique worked and had SAVED several Rubber Diaphragms with ""Worn-out Areas"" and a few with ""Split Rubber Holes"

Since this first appeared I have tried some new twists to the original fix.
Most notably: Using Glue Stick. A staple found in Craft Stores to rub on the Funnel to keep the Diaphragm Rubber firmly mounted to the Funnel.


Diaphragm Rubber Repair:

Clean the Rubber with isopropyl alcohol.
Apply MASKING TAPE to hold the OPPOSITE SIDE of the Repair.
(Holding the tear together > Perfectly.
Cut a small Funnel to act as a form.
Tape the Rubber to the Form.
(( Or smear Funnel with Glue Stick ))**
Make sure Rubber is not buckled or wrinkled.

Salvage some "Repair Material"
(I used a small section of Material cut from a Nylon Windbreaker)
(( HUGE Balloons from Party Stores will substitute.))

Cut-out a PATCH of Repair Material to COVER the TEAR.
Coat the Rubber over the TEAR with a thin coat of LIQUID Electrical Tape.

>> Quickly apply the Patch with TWEEZERS and "Iron-Out" any Air Bubble or wrinkle with a BIC Ball Point Pen (Cover and Blunt End)
Smooth-out Patch.
You don't get much time to do this.

(( You have to work fast. You have to use Fresh Product. You need a Working Surface to ""Start Fresh"" from, ... a Legal Pad lets you rip-off the former work surface and start clean))

Make a Tool out of Coat Hanger that you can DIP into the UNCOVERED Liquid Tape and DRIP some FRESH Product onto your WORK Pad.))

Once Dry:
Apply 2nd Coat of Liquid Electrical Tape.
When 1st side is dry ... repeat process on other side of Rubber ...
BUT
Don't Stick Tape on the Repair ... Just Smooth the Diaphragm Rubber Out.

((This is where the Glue Stick on the Funnel saves a lot of time and lets you ADJUST the Repair Section to get it just right))

November 23, 2009
"The RickCoMatic Patch"